Polymeric tin mercaptides

ABSTRACT

POLYMERIC TIN MERCAPTIDES OF STRUCTURE:   WHERE R1 IS THE HYDROCARBON RESIDUE OF A CYLOALIPHATIC DIMERCAPTAN, R2 AND R3 ARE ALKYL GROUP OF 4 TO ABOUT 10 CARBON ATOMS, AND X IS AN INTEGER FROM ABOUT 2 TO ABOUT 10. THE COMPOUNDS OF THE INVENTION ARE USEFUL AS NON-TOXIC THERMAL STABILIZERS FOR POLYMERS SUCH AS POLYVINYL AND POLYVINYLIDENE HALIDES.   -(S-R1-S-SN(-R2)(-R3))X-

United States Patent 3,646,081 POLYMERIC TIN MERCAPTIDES Bernard Buchholz, Blue Bell, Pa., assignor to Pennwalt Corporation, Philadelphia, Pa. No Drawing. Filed Sept. 22, 1969, Ser. No. 860,094 Int. Cl. C07f 7/22; C08t 45/56 U.S. .Cl. 260-429.?

Claims where R is the hydrocarbon residue of a cycloaliphatic dimercaptan, R; and R are alkyl groups of 4 to about carbon atoms, and x is an integer from about 2 to about 10. The compounds of the invention are useful as non-toxic thermal stabilizers for polymers such as polyvinyl and polyvinylidene halides.

i s-a -s- Tin compounds have been reacted with mercaptans and with dimercaptans heretofore to make tin mercaptides, but a new class of polymeric tin mercaptides has now been found which have surprisingly low toxicity properties.

Organotin compounds are known to have highly toxic properties and have therefore found uses as bactericides, fungicides, insecticides and other biocidal uses. However, such tin compounds must be handled with care because they also, in general, have very high animal and human 30 toxicity. Discussion of the high toxicity or organotin compounds will be found in the Tin Research Institutes publication Investigations in the Field of Organotin Chemistry (1955) by I. G. A. Luijten and G. J. M. van der Kerk.

Numerous applications for organotin compounds in polymers have been disclosed. For example, organotin compounds appear to have an excellent stabilizing effect on polymers, as for example, thermal stabilization of polyvinyl chloride, where tin mercaptides are particularly eflFective. The high human toxicity of tin mercaptides, however, 5 has hindered commercial use, particularly in plastics for food applications. In fact, only one tin mercaptide with FDA clearance is available for commercial use as a vinyl stabilizer and that is the compound di(n-octyl) tin S, S'- bis(isooctylmercaptoacetate),

(ll'cgH q 28H C l-I 2 s R1 -s -s where'R is the hydrocarbon residue of a cycloaliphatic dimercaptan, R and R are alkyl groups containing from four to about ten carbon atoms, and x, which indicates the polymeric nature of the compounds, is an integer from about2 to about 10.

The saturated hydrocarbon residue of a cycloaliphatic 3,646,081 Patented Feb. 29, 1972 fa C6 dimercaptan, R will preferably be derived from a cyclodiolefin by reaction with H 8 to yield the dimercaptan.

Thus, for example, vinylcyclohexene will add H 8 in the presence of free radical catalysts, such as ultraviolet light, gamma radiation, peroxides or azo compounds, as follows to give vinylcyclohexene dimercaptan:

CH=CH CHZOHZSH CH CH SH 2H2S H and/or II In a similar manner d-limonene or dipentene react with H 8 as follows to give d-limonene dimercaptan or dipentene dimercaptan:

CH3 CH 2mg C(srr U H a t.. on. oH. CH. CHzSH The preferred compounds of the invention will be of structure:

s l rl s H R SSn where R, is lower alkylene, R and R are defined above, R is H or lower alkyl and x is 2 to 10.

In making the polymeric compounds of the invention, the above described dimercaptans are reacted with a dialkyltin oxide of salt; e.g.

where R and R are defined above and X is a salt anion such as halide (e.g. chloride, bromide, etc.), acetate, and the like. R and R may be C to C alkyl, such as butyl, hexyl, octyl, and the like. Reaction is usually carried out in a refluxing aromatic solvent (e.g., benzene, toluene, xylene, etc.) and when a tin salt is used, an acid acceptor such as sodium carbonate is generally added. The following examples will illustrate the preparation of the compounds of the invention:

EXAMPLE I Dibutyltin vinylcyclohexene dimercaptide (A) From dibutyltin oxide (IJIHFI CHQCHQSH CH CHzSISH +H2O (04110 8110 -b H HS .s

a L r, A solution of 21.65 g. (0.123 mol) of vinylcyclohexene dimercaptan and 30.56 g. (0.123 mol) of dibutyltin, oxide in 350 cc. of toluene was refluxed until water was no longer formed, as determined with a Barrett water trap. The toluene was removed, giving 48.8 g. (97.5%) of viscous, pale yellow product soluble in ether, benzene, acetone, hexane, insoluble in water and ethanol and having a refractive index of 1.5804 D Molecular weight determination is difiicult because of dissociation in the solvents used for measurement, but the results indicated x had a value of at least 2 or 3.

Analysis.Calculated (percent): C, 47.2; H, 7.9; S, 15.7; Sn, 29.1. Found (percent): C, 47.4; H, 8.3; S, 15.5; Sn, 28.2.

(B) From dibutyltin diacetate CHzCHzSH CHzCHzSSn L x A mixture of 22.96 g. (0.13 mol) of vinylcyclohexene dimercaptan, 45.7 g. (0.13 mol) of dibutyltin diacetate and 15.7 g. of sodium carbonate, in 400 cc. of toluene and 25 cc. of water was refluxed for 6 hours, filtered, washed with water and the toluene was removed to give 52.5 g. (99%) of the product as a viscous, pale yellow residue as described above.

Calculated (percent): C, 47.2; H, 7.9; S, 15.7; Sn, 29.1. Found (percent): C, 47.15; H, 8.11; S, 15.44; Sn, 28.0.

EXAMPLE II Dioctyltin vinylcyclohexene dimercaptide KIJH CH SH O (CSHUhSIKO CHQ Nazcoa CaHn CH2CH2SSH 21130 13 L it Using equimolar quantities of viuylcyclohexene dimercaptan and dioctyltin diacetate and the same procedure as in 1-B above, the product was obtained as a viscous, yellow liquid in 88% yield. Solubility properties are the same as those of the product of Example I. Refractive index of the product was 1.5476 D and a molecular weight determination showed x to be greater than 1.

Calculated (percent): C, 55.49; H, 9.31; Sn, 22.85. Found (percent): C, 55.56; H, 9.49; Sn, 21.9.

EXAMPLE III Dibutyltin d-limonene dimcrcaptide CH CH SH Eduimolar quantities of d-limonene dimercaptan and dibutyltin oxide were reacted as in 1-A above, to give an 87% yield of the viscous, pale yellow product having a refractive index of 1.5658 D Molecular weight determination in a benzene solution gave a value of 836 which decreased with time, indicating gradual dissociation of the polymeric product in the solvent (benzene).

Analysis.Calculated (percent): 49.66; H, 8.34; S, 14.7; Sn, 27.3. Found (percent): C, 48.3; H, 8.36; S, 13.6; Sn, 26.6.

EXAMPLE IV Dioctyltin d-limonene dimercaptide CH3 CHQSH E CaHu CH CHgS n-- TABLE I 1 15 211 iH CHzS-SH aHu 'Ioxleity in mice of (A) Acute oral toxicity Method I.Administered as an aqueous emulsion (in 15% polysorbate 20 plus 6.7% Arlacel C) by stomach tube to make CF; mice, :22 g. BW. Animals observed 7 days post-dosage.

Results:

No. mice, Mortality, Oral dose, gJkg. dead/total percent NOTE.LD 10.0 grams/kg. Symptomato1ogy=N one.

Method Il.Administered as a 40% solution in corn oil by stomach tube to ten CF, mice, 23: g. BW, at a single dosage level of 10 grams/kg. Animals observed seven days post-dosage.

Results: No signs of toxicity were seen among any of the treated animals. Although minor losses in body weight occurred for several days after dosage, these were recovered fully during the seven day observation period.

Conclusions: Nontoxic at 10 grams/kg.

(B) Acute subcutaneous toxicity in mice S.c. dose, No mice, Morality, Time for c/kg. dead/total percent death, days 1 Solvent ccJkg.

NorE. LD5o= 10grams/kg.;Symptomology= Gradual losses in body weight until death.

In similar toxicity tests with the compound of Example I, the compound showed an -LD value of 1.4 grams/kg. (also a surprisingly high LD value) but did cause jaundice after 48 hours.

The compounds of the invention are of value as thermal stabilizers for polymers, particularly vinyl halide and vinylidene halide polymers and copolymers. Preferred polymers which will be stabilized with the compound of the invention include polyvinyl chloride (PVC), polyvinylidene chloride, vinyl chloride-vinyl acetate copolymers, and such copolymers as are obtained by polymerization of vinyl chloride with other copolymerizable compounds such as vinyl esters, maleates, fumarates, acrylates, methacrylates and others.

Evaluation of the compounds of the invention follow:

Evaluation as PVC stabilizers-oven test Plasticized PVC sheets, 40 mils thick, containing 1.5% by weight of the tin mercaptide stabilizer were prepared on a hot (300 F.) two-roller mill using 2 parts of unstabilized PVC resin (Allieds Plaskon SG-4l4) to 1 part of dioctylphthalate and the appropriate amount (2.25 parts per hundred parts of resin (phr.)) of the tin mercaptide. Test samples, stamped from the sheets, were inserted on trays into a circulating air oven at 380 F. and the discoloration rates were observed. The degree of yellowing during the test and the time to blackening of the samples were used as the criteria to evaluate the effectiveness of the stabilizer formulations.

Metal and Thermit Corporations commercial Thermolite 31 and Thermolite 73 stabilizers, both believed to be dibutyltin bis(isooctyl mercaptoacetate) formulations, which are currently widely used for PVC non-food bottles manufacture, were used as standards for comparison in the tests.

Produg} of Example M dz '1 Corporation from- Uinutes at Thei'mo- Thermo- Product Diacetate Oxide 33 lite 31 lite 73 of Ex. I method method 0 C C 0 VP Y Y Y Y VP Y Y Y Y LY Y Y Y Y Y Y Y A Y Y Y B Y B B B Y B B B LK B BLK BLK Color key.(.=clear, colorless; VPY=veiy pale yellow; LY=light yellow; Y=yello\v; A=ainber; B=brown; BLK= black.

The excellent long-term stabilizing effect of the products of this invention is evident from the above data.

It will be understood that the polymeric tin mercaptides of the invention may be formulated in the usual manner with other additives such as anti-oxidants, chelating agents, plasticizers, fillers, dyes, etc. The early yellowing quality of PVC stabilized with the products of this invention in oven tests as above is in fact further improved by the use of small amounts of commercially available phenolic type antioxidants in the PVC formulations. The particular advantages of the compounds of the invention reside in their excellent long-term stabilizing effects in combination with low toxicity. This permits their use in plastic containers, film, bottles and other articles which come in contact with food.

I claim:

1. Tin mercaptides of structure where R and R are alkyl of 4 to 10 carbon atoms, R; is lower alkylene, R is H or lower alkyl and x is 2 to 10.

2. A polymeric mercaptide as in claim 1 of the formula 4. A polymeric mercaptide as in claim 1 of the structure 4119-1: 5. A polymeric mercaptide as in claim 1 of the structure References Cited UNITED STATES PATENTS 2,731,484 l/l956 Best 260-429] 3,410,884 11/1968 Mack 260-429] TOBIAS E. LEVOW, Primary Examiner W. F. W. BELLAMY, Assistant Examiner US. Cl. X.R. 

